Refrigeration apparatus



May 9, 1961 J. R. BATTElGr-:R

REFRIGERATION APPARATUS 2 Sheets-Sheet 1 Filed July 5, 1956 May 9, 1961 J. R. BATTEIGER REFRIGERATION APPARATUS 2 Sheets-Sheet 2 Filed July 5, 1956 United States Patent O REFRIGERATION APPARATUS Joseph R. Batteiger, 440 Seaton St., Los Angeles 13, Calif.

VFiled July '5, 1956, Sel'. N0. 595,970

2 Claims. (Cl. 62-156) The present invention relates to refrigerating and air conditioning apparatus and more particularly to such apparatus which incorporates a mechanism for periodically circulating hot refrigerant through the components of the apparatus for defrosting purposes.

Refrigerating apparatus is known in which the expansion valve to the evaporator in the cooling compartment is either opened or by-passed to defrost the system. The compressor is then connected directly to the evaporator to permit warm gaseous refrigerant from the compressor to be circulated through the evaporator and melt the ice that is formed on its external surface during the cooling cycles of the apparatus. A problem has arisen in such systems in that it is necessary that the refrigerant circulating during the defrosting cycle be in gaseous form when it reaches the intake of the compressor. This is to avoid the slugging of liquid refrigerant through the compressor which would seriously handicap the operation of that unit.

This problem has been solved to some extent in the prior art by the provision of a second evaporator outside the cooling compartment in the suction conduit to the intake of the compressor, and by preceding this second evaporator by a second expansion valve. The additional expansion valve and evaporator operate to cause any liquid rehigerant in the suction conduit to be expanded to a gas before it reaches the intake of the compressor. However, for maximum efficiency during the defrosting cycle land to reduce the time of defrosting to a minimum, it is essential that only liquid refrigerant be fed to the additional expansion valve so that the expansion of the refrigerant and evaporation in the -additional evaporator will occur at la relatively high pressure. It is obvious that if the refrigerant supplied to the second expansion valve is half gas and half liquid, as is the case in most prior art apparatus, expansion in the second evaporator will occur `at a relatively low pressure as compared with the case in which only liquid refrigerant is fed to the second expansion valve. With relatively high pressure in the second evaporator, the gaseous refrigerant supplied to the intake of the compressor is relatively dense and at a relatively high pressure. This results in a high weight of gas pumped by the compressor per unit volume so that a high amount of latent heat is available for defrosting. It is clear, therefore, that for maximum eciencey during the defrosting cycle, liquid refrigerant onlyshould be supplied to the second expansion valve.

An object of the present invention is to provide improved refrigerating and air conditioning apparatus in which the refrigerant is fed to the compressor in gaseous form during the defrosting operation and at .a relatively high pressure and density for reduced defrost time yas compared with prior art systems. This may conveniently be achieved by the provision of a second receiver in the suction line in front of the second expansion valve and second evaporator in that line, which receiver stores the refrigerant and assures that it will be fed to the second expansion valve only in liquid form.

In most prior art refrigeration installations of the type described above, the defrosting operation is initiated by by-passing the expansion valve to the main evaporator and by by-passing the main condenser and receiver. 'This enables the compressor to pump warm gaseous refrigetant directly to the main evaporator. However, when the direct path `from the compressor to the main evaporator is first established to initiate the defrosting operation, an initial drop in pressure in the refrigerant fed to the main evaporator occurs. This results in expansion and resulting cooling of the refrigerant to be used for the defrosting and thereby prolongs the defrost cycle. Another object of the present invention is -to overcome this initial cooling effect, and this may be achieved by keeping the main receiver in the connection from the compressor to the main evaporator at the start of `lthe defrost cycle, instead of connecting the compressor directly to the evaporator as in most prior art systems. This use of `the main receiver during the defrost cycle causes Warm liquid refrigerant to flow from the receiver at the start of the defrost cycle through the main evaporator to the second receiver described above. This not only prevents a drop in the pressure of the refrigerant when the defrost cycle is initiated to preclude the cooling effect described above, but the second receiver is also filled with liquid refrigerant right at the star-t of the the defrosting operation so that it is immediately prepared to feed liquid refrigerant to the second expansion valve for maximum pressure in the gaseous refrigerant fed to the intake of the compressor.

For physical s-impliiication, the apparatus of the present invention may be constructed to use only two con-' duits or pipe lines between the cooling compartment and the compartment housing other components of the system. This latter compartment shall be referred to as the machine room in the subsequent description. This use of two conduits only between the machine room and the cooling compartment, not only cuts material costs to a minimum but also simplifies the installation of the equipment.

The apparatus of the invention can also be constructed so that the electrical connections in the cooling compartment are independent of those in the machine room. This means that no electrical connections are required to extend between the cooling compartment and the machine room. This latter feature enables all electrical Wiring efficiently to be made at the factory rather than in the field.

Most refrigerating systems include a drain pan associated with the main evaporator and it is desirable during the defrosting operation to remove any ice that might have formed in this pan. Therefore, it is usual to provide some means for defrosting the drain pan during the defrost cycle. However, diiculties have arisen in providing a feasible system for defrosting the drain pan which does not have a tendency to refrigerate the drain pan during the refrigerating cycle. An ancillary feature of the present invention is the provision of a defrost coil around the drain pan and the positioning ofthe defrost lay-passing valve at the outlet of this defrost coil `and at the junction of this coil and the coil of the mainl evaporator. When the defrost valve is closed, as it is during the refrigerating or cooling cycle, it retains refrigerant in the coil around the drain pan at high pressure. Therefore, when the defrost valve is closed at the termination of the defrosting operation, this does not result in a reduction in .pressure in the drain pan coil which would produce the undesired refrigerating effect in the drain pan due to refrigerant expanding in that coil.

Other obvious features and advantages of the refrigerating system of the invention will become evident as the description proceeds.

In the drawing:

Figure l illustrates in somewhat schematic form one embodiment of the improved refrigerating apparatus of the invention; and Y Figure 2 shows a second embodiment ofthe apparatus of the invention.

The embodiment of the invention Villustrated in Figure 14 includes a plurality of componentsv that are grouped in a machine room 10, and it includes another group of components which are positioned in a cooling compartment 12. The components in the cooling compartment 12 include Va main evaporator 14, and thisA evaporator comprises a coil 16 and a series of fins 18Y associated with. the. coil. 22, is positioned to circulate around the main evaporator 14. air, water or other duid that is to be cooled. A second coil 24 is connected to the coil 16 of the main evaporator, and'this second coil surrounds the drain pan of the evaporator and is used to defrost and removeany ice ordefrost that might have formed in the drain pan duringy the refrigerating cycle.

A defrost valve 26 is positioned at the outlet of the drain pan defrost coil 24 and at the junction of the coil 24v and the main evaporator coil 16. This valve in the illustrated embodiment is of the solenoid actuated type, and the valve opens whenever the solenoid section of the valve is energized. An inlet pipe line orconduit 28 extends into the cooling chamber 12, and a iirst branch 28d of this conduit isjoned to the inlet end of the drain pan defrost coil 24. A second branch 28h of the inlet conduit 23 extends into a heat exchanger 30 (which will be` described) and through the heat exchanger to a dehydrator 32. The branch 28b of the inlet conduit then passes through a solenoid operated valve 34 (Whose function will be described) to an expansion valve 36. The expansion valve 36 may be of any well known type and may, for example, vbe a thermostatic expansion valve having a feeler tube 38. "l'he tube 38 is mounted on a suction conduit 40 extending from the outlet of the coil 16 of the evaporator 14. The tube 38 regulates the expansion valve 36 in response to temperature variation of conduit 40 and in a manner well understood by those skilled `in the refrigeration art. The expansion valve 36 is connected between the inlet of the coil 16 of the main evaporator 14 and the outlet of the drain p an defrost coil 24.

The outlet of the coil 16 of the main evaporator 14 is connected to the suction conduit 40 as noted above, and this conduit passes through the heat exchanger 30. The suction conduit 40 is formed into a coil 40am the heat exchanger, and this coil surrounds the portion of the branch 28b ofthe inlet conduit 28 within the heat exchanger. VThe suction conduit y40 then passes out of the cooling compartment to the machine room 10.

The cooling compartment includes a pressure-timer sw-itch 42. Switches of this type are known to the industry and are available on the market as a unit. Briey, the switch 42 includes. an electrically energized timer which may be set to cause the -unit to Vbreak a normally closed connection between contact a and contact b, and to make a normally open` connection between the contact a and contact 0. This occurs after a predetermined time interval to which the timer is set, Then, in response to an increase in pressure in the conduit 44 above an established threshold, a pressure bellows is actuated in the switch 42 which restores the original con-V nection between contacts a and b.

The cooling compartment 12, has a pair of input terminals 46 which may be connected to any suitable energizing power source. One of the terminals 46 is conrrectedA to the contact a on the pressure-timer switch 42, andthe other of these terminals is connected to one terminal of Vthe solenoid valve 26 and to oney terminal of the motor 22 of the fan 20. The contact b of the switch A fanV 20, which4 is driven by: a fan motor` 42 is connected to, the other terminal of the fan motorV predetermined threshold. The timer in the switch 42 may also beY connectedY through the thermostat I48, so that it is energized only during intervals when the valve 34 is energized and open.

The heat exchanger 30 may'include a solid metallic block of relatively high heatconductivity surrounding the coil 40a and the portion of'the arm 28h in the heat exchanger.

v The machine Yroom 10 of the apparatus includes a usual compressor 52. lheloutlet of the compressor is connected through a conduit 53. to the coil 56 of a condenser 57. A pressure operated switch 54 of usual con struction is mounted on the conduit 53. Aseries of tins 58 are associated with the coil 56; and a fan 60, driven by a fan motor 62, may be used to circulate cool air or other condensing iluid around the condenser coil 56. The outlet of the condenser coil 56 is connected to a receiver 64 which, in turn, is connected to the conduit 28 leading to the coolingfcompartment 12.

The suction conduit 46 from the cooling compartment 12 is connected to the inlet of a second receiver 68; A pressure operated switch 66 is mounted on this conduit adjacent the second receiver. The outlet of the second receiver is connected through a second expansion valve 70 to the inlet of a coil 72 associated with a second evaporator 74. The second evaporator includes a series of fins 76 mounted on the coil 72; and a fan 78, driven by a fan motor 80, may be used to circulate warm air over the second evaporator. n

The second expansion valve 70 has the construction and function set forthV in the Kellie patent, U.S. 2,645,884, issued July 21, 1953. This valve which is known in the art as an automatic expansion type valve may be purchased from Arninco Refrigeration ProductsV Company, Detroit, Michigan, and is described by the vendor as a compressor suction throttling valve. Such a valve has an adjustable spring-loaded diaphragm counterbalanced by the fluid pressure on the outletfside of the valve to cause the valve to move from` closed position to open position in response to a predetermind pressure setting, there being a small pressure diierential existing from fully closed to fully open, say, a pressure differential of 2 pounds p.s.i. During the defrost cycle the higher pressure passing through the orifice of the valve allows the valve to modulate and expand the liquid refrigerant into a gaseous state. Y

A by-pass conduit 82 is provided between the suction conduit 40 and the outlet of the coil 72 of the evaporator 74. The conduit 82 by-passes, the receiver 68, the expansion valve 70 and the evaporator 74. A solenoid operated valve 84 is positioned in the by-pass conduit 82, and when this valve is energized it operates to close the by-pass conduit. The upper end of the by-pass conduit is connected to the outlet of the coil 72 of the evaporator 74 by a T-joint 86. This joint is positioned yto have its section leading to the evaporator 74 disposed on a vertical axis, so .thatV any liquid refrigerant that might pass through the liquid by-pass conduit 82 will fall by gravity into this evaporator and will not pass to the compressor 52. The youtlet of the joint 86 is connected through a conduit 87 to the intake of the compressor. A pressure operated switch 88 is mounted on the conduit 87.

The machine room 10 has a pair of input terminals 90 whichl are connected to a suitable power source. One of these terminals is connected directly to the motor 62 of the fan 6l) associated; with the condenser 57 and the other is connected to this fan motor through theV pressurey operated switches 88 and 54. Likewise, one of these terminals is connected directly to solenoid valve 84 in the by-pass conduit 82 and to the fan motor 80 of the fan 78 associated with the second evaporator 74, and the other input terminal 90 is connected to these latter units through the pressure operated switch 66.

The arrangement is such that when the pressure at the inlet of the condenser drops below a certain threshold so as to indicate a defrost cycle, the switch 54 responds to this decreased presure to deenergize the condenser fan 60 associated with the condenser 57. Also the switch 66 at the inlet to the receiver 68 responds to a corresponding increase in pressure in the suction conduit 40 at the start of a defrost cycle to energize and close valve 84 in the by-pass conduit 82 and to energize the fan 78 associated with the evaporator 76.

One of the terminals 90 is also connected to the motor driving the compressor 52, and the other terminal is connected to the motor through the pressure operated switch `88. As previously noted, the pressure operated switch 88 is positioned at the intake of the compressor, and the compressor motor is energized whenever the pressure at its intake rises above the selected threshold so as to close the switch 88 and energize the compressor. Also, because the switch 88 is in the energizing circuit to the condenser fan 62, this fan is not energized when the compressor is not energized.

When the apparatus is conditioned to be cycled in a series of cooling operations, the defrost solenoid valve 26 in the cooling compartment is in a deenergized and closed condition. If the temperature is below the desired level, the solenoid valve 34 is also in a deenergized and closed condition. The fan 20 associated with the main evaporator 14 is energized to circulate the huid to be cooled around the evaporator. In the machine room, the pressure operated switch 54 is closed, but the condenser fan 60 is not energized to circulate condensing uid around the condenser 57 because the switch 88 is open. Also, the fan 78 of the evaporator 74 and the solenoid valve 84 in the by-pass conduit 82 are deenergized,

Now, assuming that the temperature in the cooling compartment 12 rises to a value sufficient to initiate a cooling cycle. Then the thermostat 48 closes a circuit to the solenoid valve 34 opening that valve. This permits gaseous refrigerant to ow through the expansion valve 36 to i the evaporator14 and then to the suction line 40. This refrigerant is a saturated gas at the outlet of the evaporator 14. The pressure of this refrigerant is not sufficient to operate thev pressure operated switch 66 so it travels up the by-pass conduit 82. However, it has suiiicient pressure'to operate the switch 88 which is set to a lower pressure threshold than the switch 66, and the compressor 52 and the condenser fan 60 are energized.

The compressor now compresses the gaseous refrigerant and supplies the compressed gaseous refrigerant to the condenser 57. The fan 60 is in an energized condition and it circulates a condensing coolant around the condenser so that the compressed gas from the compressor is cooled and is condensed into a liquid that accumulates in the receiver 64.

The liquid refrigerant is forced from the receiver 64 through the conduit 28. The flow of the refrigerant through the branch 28a into the coil 24 of the drain pan is arrested by the closed defrost valve 26. However, the liquid refrigerant from the conduit 28 ows down the branch 28b and through theheat exchanger 30. It is cooled in the heat exchanger by the refrigerant leaving the main evaporator 14 in the suction conduit 40. The cooled liquid refrigerant from the heat exchanger 30 passes through the dehydrator 32 which removes any Wate'r in the refrigerant, and it then passes through the open valve 34 to the expansion valve 36. The expansion valve 36 operates in known manner to cause the refrigerant to expand into the low pressure evaporator coil 16.

This expansion converts the liquid refrigerant to a gas and causes -it to absorb its latent heat of evaporation from the fluid circulated around the evaporator by the fan 20 so as to cool that uid. The refrigerant leaves the coil 16 of the main evaporator "14 as a saturated gas. It then passes through the coil 40a and absorbs heat from the liquid refrigerant in the branch 28b. The gaseous refrigerant in the conduit 40 does not have suicient pressure to operate switch 66 and hence passes through the by-pass conduit 82 and through the conduit 87 to the intake of the compressor 52.

As the refrigerating cycle progresses, the gaseous refrigerant circulated through the system becomes cooler and cooler, and the pressure of the gaseous refrigerant in the suction conduit 40 and in the by-pass conduit 82 becomes lower and lower. When the temperature in the cooling compartment drops to a desired level, the thermo stat 48 deenergizes and closes the solenoid valve 34 to terminate the cooling cycle. This stops the ow of refrigerant. The compressor continues to operate until the pressure at its intake is reduced to a point such that the pressure operated switch 88 is operated to deenergize the compressor and condenser fan. None of the other electrical equipment in the machine room is aected `by this because neither the switch 84 nor the switch 66 were operated during the cooling cycle. Therefore the by-pass conduit 82 remains open.

The operation of the system is now suspended until the temperature in the cooling compartment 12 again rises to a level sucient to operate the thermostat so that another cooling cycle may be initiated. In this manner, the thermostat 48 is effective to cycle the compressor 52 in the machine room lwithout the need for interconnecting electrical wiring and to initiate a cooling cycle each time the temperature in the cooling compartment rises to a predetermined level. The thermostat 48 and its associated solenoid 34 are not essential, because the switch 88 will stop the compressor Whenever the pressure of the refrigerant drops below the threshold of this switch. The pressure of the refrigerant drops with the temperature of the cooling compartment, and the threshold of the switch 88 can be set to cut olf the compressor :whenever a desired temperature -is reached.

The timing of the defrosting operations is controlled I by the pressure-timer switch 42. The timer in this switch 42 may be directly energized from the terminals 46 so that the defrosting occurs at regularly timed intervals. However, it is preferable to energize the timer through the thermostat 48 so that the defrosts are made to depend upon the actual total time of the cooling cycles, rather than merely on total elapsed'time. This more closely relates the occurrence of the defrosting operations to the time that such defrosting is actually required. As noted previously, to linitiate a defrosting operation, the switch 42 breaks the connection between its contact a and its contact b and makes a connection between contact a and contact en This causes the fan 20 associated with the main evaporator to be deenergized, and the defrost solenoid valve 26 to be energized.

*When the above occurs, the warm liquid refrigerant from the receiver 64 passes through the conduit 28 and through the branch 28a and the drain pan coil 24. The liquid refrigerant then passes through the valve 26 to the evaporator coil 16 warming that coil to melt the frost that has formed on its external surface. The liquid refrigerant, now somewhat cooled, passes from the evaporator coil and through the heat exchanger 30 to the suction conduit 40. The 4liquid refrigerant passes through the'heat exchanger but is not affected by it to any appreciable extent as the incoming refrigerant is now passing through the branch 28a rather than the branch 28b through the heat exchanger.

'I'he pressure created by the liquid refrigerant in the 78 suction line 40 on the pressure operated switch 66 causes the switch to close the by-passconduit 82 by energizing the valve 84; and, at the same' time, the switch 66 energizes the fan 78 associatedwith .the second evaporator 74. The energizing of the fan 78 initiates a flow of warm fluid around the evaporator 74.

' The liquid refrigerant now accumulates in the receiver 68 and is forced through the expansion valve 70V to the evaporator 74.v The refrigerant expands to its gaseous state in the evaporator 74 andis fed to the intake of the compressor 52. The pressure of the gaseous refrigerant now passing the pressure switch 88 maintains the cornpressor energized, but the pressure of the gaseous refrigerant now issuing from the compressor is not high enough to maintain `the switch 54 in its former state, and this switch is actuated to deenergize the fan 60 associated with the condenser v57. This terminates the :dow of coolant around the condenser by the fan 60. The gaseous refrigerant from Ythe compressor 4is now no longer condensed in the condenser 57. This is because of the reduced pressure at this point in the system and because of the reduced heat-exchanger eiect due to the fan being deenergized. The hot gas from the compressor passes through the receiver 64 into the conduit 28 to be circulatedthrough thev drain pan coil 24 and through the evaporator coil 16 until the defrosting operation is completed. This gaseous refrigerant is cooled in the evaporator and emerges in the conduit 46 in essentially liquid lform. This liquid refrigerant passes through the now ineective heat exchanger 30 and it is accumulated in the receiver 68. The liquid refrigerant is then passed through the expansion valve 70 tothe evaporator 74 where it once more expands to a gas and is fed to theV intake of the compressor 52. This circulation continues throughout the defrosting operation.

As thedefrosting operation progresses, the pressure at the outlet of the evaporator 14 continues to increase as the temperature rises and the switches 66, 88 and 54 do not change position. At the completion of the defrosting, the pressure of the refrigerant rises to a point such that the pressure in the conduit 44 causes the bellows in the switch 42 to be actuated to disconnect the the connection of the contact a from c.and return it to its Original contact with contact b. This causes the defrost solenoid valve to close and the main evaporator fan 20 to be energized. The system is then prepared .to reinitiate a series of cooling cycles. Now the refrigerant in the conduit 28 can no longer pass through the branch 23a and it passes through the branch 28b to the expansion valve 36. The expansion valve causes the refrigerant to expand in the evaporator 14 cooling the same. As the cooling progresses, and as the balance of refrigerant in receiver 63 is evaporatedthrough eX- pansion valve 70, the pressure in the suction conduit drops to return the switch 66 to its original condition. This Ydeenergizes the valve 84 to open the by-pass conduit 32 and also deenergize-s the fan 78 associated with the second` evaporator 74. The pressure of the refrigerant is still too high to actuate the switch Vil'and the compressor S2 continues to be energized. Also, the pressure now is sufficiently high to operate the switch 54 and the con-A denser fan 6i) is again energized. Now the system is operating with full cooling etciency.

When the temperature of the Vcooling compartment drops to .the desired level, the compressor is deenergized. This is either under the control of the valve 34 in turn controlled by the thermostat 48, as previously described, and/ or under the control of the reduced pressure of the circulating refrigerant on 'the switch 88 as also explained previously. Y

' It will be observed, that when the defrost cycle is initiated in the system described, the receiver 64 is not by-passed, but is connected directly to the evaporator coil 16 through thev deost valve 26. This causes the liquid refrigerantfrom the receiver 6.4 to flow through the evaporator 14 to the receiver 68 at the beginning of the defrosting ope-ration so that there is no preliminary pressure dropV in the refrigerant when this operation is initiated. Such a pressure drop occurs in systems in which the compressor is directly connected through the defrost valve to the main evaporator for defrosting, and it produces a corresponding cooling effect which prolonge the defrosting operation.

The use of the second receiver 68 in the described systcm provides a storage'for the initial How of liquid refrigerant described in the preceding paragraph, and this receiver assures that only liquid refrigerant is introduced to the expansion valve 70. This assures that the refrigerant in the evaporator 74 will be a relatively dense gas so that the compressor 52 will produce optimum weight of gaseous refrigerant at -unit volume. This provides optimum latent heat so rthat the deosting operation proceedsl at maximum eiliciency and the defrosting is completed in minimum time.

It should also be noted that the control switches in the machine room respond to changes in pressure in the com duits and there is no wiring between the cooling compartment and the machine room. Also, the only connection between these two compartments are the two conduits 28 and 40, which reduces materia-l costs and which simplifies the installation of the equipment as compared Y outlet of the drain pan coil 24 provides that when this valve is closed to reinitiate a refrigerating or cooling cycle after a defrosting operation, aV high pressure is created in the drain pan coil, rather than. low pressure. There is, therefore, no expansion of the refrigerant in the drain pan coil 24 at the beginning of a cooling cycle and which would produce a cooling effect and result in reigerating and forming ice and frost in the drain pan.

The apparatus of the invention can be used for walk-in or reach-in refrigerators or for cold storage rooms. Moreover, the apparatus can be used for air conditioning, with the defrosting operation being used for heating the air conditioned area when the outside temperature falls below the temperature at which the area is to be maintained.

The embodiment of Figure 2 is similar in some respects to that of Figure l and like components have been represented by like numerals.

However, in the latter embodiment, the second receiver 68 and the second expansion valve 70 have been moved to the cooling compartment, and the heat exchanger 30 is used to serve as the second evaporator. This embodiment also does not use the by-pass conduit 82Y of the embodiment of Figure l and the solenoid valve 84 in that conduit has also been dispensed with. The thermostat 48 of Figure 1, and the solenoid valve 34 actuated by the thermostat are not included in the-embodiment of Figure 2, nor is the dehydrator 32.

The main condenser 57a: in the embodiment of Figure 2 is shown as la. liquid cooled type, and the coil 56 of the condenser is surrounded by a tubular jacket 59. Cooling liquid from any suitable source is fed to one end of the jacket S9 through an inlet conduit 61. Y A solenoid actuated valve 63 and a modulating valve 65 are included in the inlet conduit 61. The cooling liquid ilows through the jacket 59 in a direction opposite to the flow of the gaseous refrigerant from the compressor 52 in the coil 56, and it emerges through an outlet conduit 67 which extends to any sm'table drain.

The modulating valve 65 is of known construction and it has a feeler tube 65a connected to the outlet conduit fromthe compressor 52. The valve 65 responds to the pressure of the gaseous refrigerant h'om the compressor to regulatejthe liquid ow through the packet 59.4` The liquid ilowinv the condenser can be controlled in this manner to be suicientat all times to Vcool and condense the gaseous refrigerant from the compressor.

The solenoid valve 63 is connected across the input terminals 90 in series with he pressure-operated switches 54 and 88 so that the cooling @liquid ows through the condenser 57a only during ya refrigerating cycle. rIhe pressure operated switch 88 in this embodiment has an additional actuating control which is connected to the inlet of the `condenser 57a and serves to operate the switch and cut oi the compressor should the pressure in the condenser rise to an abnormal level.

The heat exchanger 30 is mounted Vin a tank 31 containing any suitable liquid, and in which liquid the coil 40a and the portion of the branch 28h surrounded by the coil are submerged. An auxiliary electric heater 50 may be provided for heating this liquid during the defrost cycle, this heater being connected in shunt with the defrost solenoid valve 26. The liquid in the tank may be a eutectic solution that freezes during the defrost cycle and melts during the refrigerating cycle of the mechanism. Water, with any suitable freezing depressant such as denatured alcohol may serve for this purpose.

During a refrigerating cycle, the switch 88 energizes the compressor 52 and gaseous refrigerant is pumped to the condenser 57a.. This switch also actuates and opens the valve 63 because the switch 5'4 is closed. Therefore, cooling liquid ows to the condenser and the refrigerant is cooled and condensed. The liquid refrigerant accumulates in the receiver 64 and is forced along the conduit 28 and down the branch 28b through the heat exchanger 30 and through expansion .valve 36 to the main evaporator 14. The electric heater 50 in the heat exchanger is deenergized during the refrigerating cycle because the defrost solenoid valve 26 is deenergized. The warm refrigerant passing through the heat exchanger melts the liquid in the tank 31, and the refrigerant is cooled by this liquid and by the cooled refrigerant passing through the section 40a of the suction conduit 40. The refrigerant from the heat exchanger is expanded into the main evaporator 14 through the main expansion valve 36, and the refrigerant emerges from the main evaporator -as a saturated gas. It now passes directly to the receiver 68 and is fed through the expansion valve 70 to the heat exchanger 30. The valve 70 may be any well known type of pressure-operated expansion valve. Such a valve is described, for example, at page 144 et seq. of Modern Electric and Gas Refrigeration, Althouse, which was published in 1947 by the Goodheart- Wilcox Publishing Company of Chicago; or at page 345 et seq. of Refrigeration and Air Conditioning, second edition, Jordan and Priester, published 1956 by Prentice- Hall, Inc., Publishing Company of Englewood Cliffs, New Jersey. 'Ihe orifice of the expansion valve 70 approximates the size of the conduit 40 in which it is mounted. This permits -full ow of gaseous refrigerant during a cooling cycle. This valve preferably is of the automatic expansion valve type and is adapted to remain open until a predetermined pressure is reached and then to operate vas an expansion valve. That is, during a cooling cycle it is open to provide an unrestricted path for the refrigerant, but during a defrost cycle as the pressure rises it throttles and operates as an expansion valve. The refrigerant then passes to the intake of the compressor 52 to be re-circulated.

'Ihe refrigerating cycle continues until the cooling compartment temperature reaches a desired low value. 'Ihe corresponding low pressure of the refrigerant at the intake of the compressor 52 then causes the switch 88 to deenergize the compressor 52, and to deenergize and close the condenser solenoid 63. The system then remains dormant until the temperature of the cooling compartment rises to a value suflicient so that the pressure of the refrigerant at the intake of the compressor will be high enough again to actuate the switch 88.

When a defrost cycle is initiated by the switch 42, the defrost solenoid valve 26 is energized and opened and the auxiliary heater 50 in the heat exchanger tank 31 is also energized. As in the previous embodiment,

tively easy and inexpensive to install.

warm liquid-refrigerant flows from the receiver 64 up the branch 28a and down the drain pan defrost coil 24 i and through the solenoid valve 26 to the main evaporator 14. This liquid refrigerant is then fed to the receiver 68 and is expanded through the now throttled expansion valve 70 to the heat exchanger 30. The refrigerant then is heated by the auxiliary heater 50 and also by the latent heat from a resulting freezing of the eutectic solution, thereby expanding it to its gaseous state.

The pressure of the refrigerant at switch 88 at the intake of the compressor 52, is, of course, sufficiently high so that the compressor is continually operated during the entire defrost cycle. Also, the pressure of the refrigerant at the outlet of the compressor is low enough during the defrostr cycle to operate the switch 54 and terminate the ow of cooling liquid through the condenser for the duration of the deh-ostV cycle.

The invention provides, therefore, an improved refrigerating or coolingsystem which is eminently simple and inexpensive in its construction, and one which is rela- Moreover, the apparatus of the invention is extremely ell'icient in operation and incorporates an automatic defrosting operation which is extremely rapid so that the time required to defrost is reduced to a minimum.

Although the now preferred embodiment of the .present invention has been shown and described herein, it is to be understood that the invention is not to be limited thereto, for it is susceptible to changes in form and detail within the scope of the appended claims.

I claim:

l. Refrigerating apparatus including in combination: a compressor for raising the pressure of a gaseous refrigerant; a condenser for cooling the refrigerant from said compressor to its liquid phase; a receiver for accumulating liquid refrigerant from said condenser; lan evaporator; rst conduit means for interconnecting the outlet of said compressor to said condenser, second -conduit means for interconnecting said condenser to said receiver, third conduit means for interconnecting said receiver with the inlet of said evaporator, and fourth conduit means for interconnecting the outlet of said evaporator to the intake of said compressor; a heat exchanger unit in said fourth conduit means for coupling said fourth conduit means in heat exchange relation with said third conduit means to transfer heat from the refrigerant entering said evaporator to the refrigerant leaving said evaporator; and a second receiver and an expansion valve included in said fourth conduit means in the recited order between said evaporator and said heat exchanger unit to accumulate liquid refrigerant during a defrost cycle and to cause such liquid refrigerant to expand to its -gaseous phase in said heat exchanger unit.

2. Refrigerating apparatus including in combination: a compressor for raising the pressure of a gaseous refrigerant, a condenser for cooling the refrigerant from the compressor to its liquid phase, a receiver for accumulating liquid refrigerant from the condenser, an evaporator, a first conduit means for interconnecting the outlet of said compressor to said condenser, second conduit means for interconnecting the outlet of said condenser to said receiver, third conduit means for interconnecting the outlet of said receiver to the inlet of said evaporator, and fourth conduit means for interconnecting the outlet of said evaporator to the intake of said compressor, a second receiver, and an expansion valve and a second evaporator disposed in that order in the fourth conduit means to accumulate liquid refrigerant in the second receiver during a defrost cycle and to cause such liquid refrigerant to expand to its gaseous phase in the second evaporator for application to the intake of the compressor, fifth conduit means by-passing said second receiver and said second evaporator and said expansion valve, a solenoid-operated valve interposed in the fifth conduit means, and a pressure-operated switch interposed K Y 11v Y, Y in said fourth conduit means to axctuate said solenoidoperated valve when the `pressure of said last mentioned presSure-ogerated switch exceeds a predetermnedthreshold.

References Cited in the le of this patent UNITED STATES PATENTS 1,185,597 Eddy May 30, 1916 12 Dickens Aug. 10, 1948 Lund Oct. `19', 1948 Kirkpatrick j Dec. 7, 1948 Gygax Sept. 30, '1949 Nussbaum Nov. 21, 1950 Mattison Aug. 24, 1954 Smith Oct. 19, 1954 Topthman rNov. 9, 1954 Ashley, June 14,' 1955 

